Floyd Mayweather has already carved out a pretty significant spot in boxing history, but the 37-year-old pound-for-pound king isn’t resting on his laurels.

Already an undefeated five-division, 10-time world champion, Mayweather has participated in the two richest fights in boxing history—against Oscar De La Hoya and Canelo Alvarez—and he’s topped the Forbes list of the highest-paid athletes two years running.

Constantly seeking to push the bar further, Mayweather, a student of the game if there ever was one, may be planning something truly historic for his next contest.

World Boxing Council President Mauricio Sulaiman, per Boxingscene.com, said on Tuesday that he believes Mayweather would like to defend both his WBC Welterweight and Junior Middleweight Championships in his next fight, scheduled for September 13.

It’s a novel idea that would solidify the legacy of a fighter who, while undefeated, remains a polarizing figure. It would put him into some pretty rarified air when it comes to in-ring accomplishments.

Who he'd fight remains a significant question.

Golden Boy Promotions, who has co-promoted every Mayweather fight since 2007, somewhat remains in a state of limbo after the resignation of longtime CEO Richard Schaefer last week.

Mayweather quickly announced that he wouldn't do business with the company in the wake of Schaefer's resignation, a statement he later qualified to mean for his next fight and not necessarily permanently. It remains to be seen which fighters actually remain under contract to Golden Boy and which are just under contract with advisor Al Haymon.

Haymon and Mayweather are close, and the resolution of that issue is likely to have a significant impact on who the pound-for-pound king elects to face next.

Mayweather, like all contemporary sports stars, often runs into the same type of circular historical comparison arguments that have beguiled sports fans since the beginning of time. His supporters are quick to point out his many successes—undefeated, seldom challenged, multiple world titles and the sport’s biggest commercial star—but his detractors often point out that he hasn’t covered much new ground.

Mexican legend Julio Cesar Chavez began his career with 87 straight victories, and he didn’t lose until facing Frankie Randall in 1994, the 91st bout of his storied career.

Other legendary fighters—Muhammad Ali and Sugar Ray Robinson among others—fought in better all-inclusive eras, and they padded their resumes with fights against other elite fighters on an overall better level of competition.

We can quibble all day and night about who Mayweather did and did not face—his resume isn’t nearly as full of holes as many of his detractors would tell you—but he’s taken on many good and a few great fighters.

But even if you fall into the category of fans who believe that the pound-for-pound king fought the best available opponents—he has a habit of making quality fighters look ordinary—his level of opposition doesn’t separate him from the historical pack.

And that’s what it’s really all about for Mayweather at this late stage of his career. He only has three fights remaining on his big-money contract with Showtime, and we’re firmly into the padding legacy portion of our show.

Defending world titles in two separate weight divisions is not only practical—Mayweather is a natural welterweight who never puts on more than a couple of pounds to make junior middleweight—it’s historic.

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Plenty of fighters throughout history have moved up in weight and captured a world title, but nobody, at least in the era of sanctioning organizations and multiple belts per weight division, has ever defended two belts from different weight classes in the same fight.

Nobody.

Nada.

Not one.

The closest we’ve come was when Sugar Ray Leonard and Donny Lalonde met in 1989 for the WBC Light Heavyweight and Super Middleweight Championships, which was newly created and vacant at the time.

Leonard stopped Lalonde in Round 9, capturing both titles simultaneously. But he didn’t stick around long at light heavyweight, choosing to vacate the title and campaign in defense of his 168-pound crown.

Going further back in history, Henry Armstrong held world titles in three divisions at the same time.

Homicide Hank held the featherweight, lightweight and welterweight world championships at the same time.

Armstrong bounced between weights—mostly from lightweight to welterweight—during his legendary run, but he mostly focused on defending his welterweight title.

And that leaves Mayweather with a golden opportunity to stake out some ground in boxing history that belongs only to him. It gives him the chance to seize that one moment, that one accomplishment that many observers feel is lacking from his overall resume.

It’s the chance to do something that has never been done before, and it’s the chance to add some serious points to a legacy that remains the subject of debate in many circles.

For Mayweather, already a legend and future Hall of Famer, this could be the moment of immortality. The moment to silence, insofar as this is possible, many of his critics.